This study was undertaken to determine the clinical efficacy of trivalent inactivated influenza vaccine in the prevention of influenza infection and illness in young, healthy, hospital staff, and to determine the extent of reduction in absenteeism in this group as a result of receiving the vaccine. This is the third winter we have undertaken a study of the efficacy of the influenza vaccine in hospital staff. We enrolled a total of 156 adults in our study, 60 males and 96 females. Blood was drawn from each subject at the time of enrollment and again one month later. We began intensive surveillance on December 22, 1994 when the influenza epidemic appeared to start, telephoning each subject weekly to inquire about flu- like illness. Throat cultures were obtained on a total of 47 of the subjects who developed symptoms consistent with influenza. We continued surveillance for fourteen weeks, ending March 29, 1997 when sporadic febrile flu-like illnesses appeared to be diminishing in house officers. A final blood sample was obtained from all study subjects one month later. We attained 99% follow-up. We therefore had a total of 15288 days of observation of the house officers. The serological data is expected from the laboratory soon and is not available for this report. The results of this study thus far have been largely inconclusive. The first year the entire United States had a very mild influenza season. This second year other parts of the United States experienced a rather severe influenza season but Baltimore and most of Maryland had very little influenza reported. We await the serological data from the third winter.